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Effects of a temperature shift on seawater challenge test performance in Atlantic salmon (Salmo salar) smolt

Abstract

Seawater tolerance of Atlantic salmon (Salmo salar) smolts acclimated at 8 degreesC in fresh water was tested in seawater challenge tests at 2 degreesC, 5 degreesC, 11 degreesC, 14 degreesC and 17 degreesC, and compared to a test at 8 degreesC. Two tests were used, a 24-h, 35 parts per thousand and a 24-h, 40 parts per thousand salinity test. In 35 parts per thousand salt water, there were no differences in plasma Cl- concentrations in the range 5-14 degreesC (mean values 140-144 mM). An increase in plasma Cl- level was found at 2 degreesC and 17 degreesC (mean values about 155 mM). The mean Cl- concentration at 8 degreesC in 40 parts per thousand test was 10 mM higher than that at the same temperature in 35 parts per thousand salinity. An increase in plasma Cl- level was found when the temperature shifted from 8 degreesC to either 5 degreesC or 14 degreesC (mean values 171 mM), and an even larger increase was recorded at 2 degreesC (mean value 209 mM, 75% mortality) and 17 degreesC (mean value 194 mM).

The results indicated that smolt had the ability to hypoosmoregulate over a wide range of temperatures when transferred to full-strength sea water. However, differences from the acclimation temperature larger than 4-6 degreesC are not recommended, especially when the seawater temperature is lower than in fresh water. The use of a higher salinity than that of full-strength sea water may give a more comprehensive picture of the hypoosmoregulatory ability of smolts, and may possibly be used to distinguish differences in hypoosmoregulatory capacity of smolts not readily obtained from tests in full-strength sea water. (C) 2001 Elsevier Science B.V. All rights reserved

Category

Academic article

Language

English

Author(s)

  • Magne Staurnes
  • Trygve Sigholt
  • Torbjørn Åsgård
  • Grete Bæverfjord

Affiliation

  • SINTEF Ocean
  • Nofima, The Norwegian Institute of Food, Fisheries and Aquaculture Research

Year

2001

Published in

Aquaculture

ISSN

0044-8486

Publisher

Elsevier

Volume

201

Issue

1-2

Page(s)

153 - 159

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